Further to Dustins's comments about the outer focus points. I love my 6D but I now have a clearer awareness of the shortcomings of the AF.
Thinking about what Canon did to handicap 6D shooters disappoints me. It seems to me a significant number of shots in vertical orientation will involve a live subject that is tall that you are trying to fill the frame with. Maybe a person with focus on the eyes or my sapsucker in a similar situation. The outer focus point gets more easily confused and if the subject is moving then there isn't always time to recompose using the center point, which is superb. Why couldn't they have made just the far right and the upper point double cross - seems a no-brainer to me??
As others have said, the 6D and wildlife leaves one just a little disappointed, more so because the camera is otherwise such a treat. Still, no regrets because the near future will have what I'm looking for (hopefully) and the 6D will be my second body.
I've yet to have any problems with servo tracking using the outer AF points on the 6D, even in low light with an f/4 lens (usually this is people walking around, or slow moving wildlife...not birds in flight). As for wildlife specifically on any of my telephoto lenses, I mostly use the center point.
As I have mentioned in the other thread, I don't see Canon as "handicapping" the 6D's autofocus. They simply did not want to use the 7D's sensor (it is aging and needs more processing power than they wanted to include with the 6D). So instead they came up with a new one, or at least a new variation of the old one used in the 5D2. It works as good or better than the 5D2's, especially the center point.
Canon certainly was not going to give the 6D a more sophisticated AF sensor, and keep the price where they wanted it. If it did have a better sensor, it also certainly would have impacted, if not killed sales of the 5D3. But to offer the 6D with that mythical AF sensor that some of you think you need, would have meant the price for the 6D body would have been too similar to the 5D3's price anyway. It would not have been able to compete with the Nikon D600 as easily, because its price would have been higher (rather than lower
in most of the world). It would not be a product that fills a price point within the product line.
Therefore it was never going to happen. To complain about the AF ability of the 6D is silly. It works fine, if you take the time to try to use it correctly.
Jack, you need to lend me that 300 ii for a few weeks, because I think you are too disappointed, and we can't have that!